Device for reducing the tension of the film in cinematographic apparatus



Aug. 23, 1932.

DEVICE FOR REDUCING THE TENSION OF THE FILM-IN CINEMATOGRAPHIC APPARATUS Filed March 9. 1929- 5 0e mum E. OEHMICHEN 1,373,463

Patented Aug. 23, 1932 UNITED STATES ETIENNE OEHMICHEN, OI VALEN'TIGNEY, FRANCE i DEVICE FOB'BEDUCIN G THE TENSION OF THE FILE IN CIHEHATOGRAPHIG APPARATUS Application filed March 9, 1928, Serial Ho. 845,648, and in France June 20, 1928.

This invention relates to the devices which are used for reducing the tension of the film in cinematographic apparatuses and particularly to the devices of the kind described in flthe application No. 223,822 filed the 3rd of October 1927.

The said devices comprise one or several friction surfaces whose position is selected in such manner that the portion of film ineluded between one of the supplying toothed barrels revolving at a uniform rate and the respective unwinding or winding spool freely passes over this friction surface when it is loose and bears and rubs upon the said surface "T when it is taut.

The. present invention relates more particularly to the friction surface or surfaces which are situated between the supplying drum or barrel located at the outlet of the W channel, the cinematographic apparatus and the spool about which the film is going to wind itself, the said friction surfaces being used for braking the film when the same is drawn too quickly by the winding spool.

According to this invention, use is made of a rotary friction organ operatively connected to the said supplying barrel or drum so that its periphery will have imparted thereto a linear speed which will be proportional to the speed of the said barrel and consequently to that of the film.

This arrangement shows relatively to the use of unmovablc braking surfaces, the advantage of avoiding the localized wear which takes place on the latter, as the contact points of the revolving friction organ with the film are continuously changing whilst the wear is very regularly distributed all round the said organ.

Moreover, on account of the proportion ality-existing between the rates or speeds of the film and the friction surface, the efficiency of the device remains constant whatever may be the rate at which the operator causes the apparatus to move.

The accompanying drawing shows, by way of example, an embodiment of the object of the invention.

Fig. 1 is a side elevation of the braking device.

Fig. 2 is a section made along the axis of a revolving braking organ.

1 denotes the projection apparatus; 2, the film; 3, the outlet delivery device which, for the sake of clearness, has been supposed to be of a diameter equal to the one of the braking drum or barrel 4; 5 and 6 are loose rollers 7 is the winding spool; 8, a transmission of any sort, a chain for instance assing over toothed wheels 9 and 10 connected to the delivery device and the braking drum or barrel. The radius of the toothed wheel 9 being smaller than the one of the wheel 10 and the diameter of the braking drum 4 being equal to the one of the delivery or supplying device 3, the surface s eed of the drum or barrel 4 is smaller than t e speed of the film which is itself equal to the surface speed of the supplying device 3. Of course thesupplying device and the braking barrel can be connected through any other transmission means so that their rates of rotation will constantly be proportional.

I It is obviously possible toprovide for several drums or barrels such as 4 and loose guiding rollers such as 5 and 6, disposed in such a manner that the film successively passes about the said drums orbarrels in fol- 4 lowing a sinuous path, all of the said drums or barrels revolving at a same linear speed which is proportional to the one of the film. In a general manner, use is made of one or several barrels 4 the surface speed of which is somewhat less than that of the film, for example nine-tenths of the said speed, so that when the film comes into contact with the said drum or drums, the required braking action takes place. This braking action can also be obtained when the connection between supplying device 3 and the drum or barrel 4 is such that the surface speed of the barrel is in a direction opposite to that of the film. In this case, the surface speed of the drum or barrel 4 can be of any range.

Fig. 2 shows a preferred construction of the braking drums or barrels. 11 shows a shaft connected with two cheeks 12 andv 13 which are provided with rings 14 made of a is high relatively to the film, such as indiasubstance the coefiicient'of friction of which I rubber, for example; 15 is an intermediate loose barrel the edges of which are approxi mately flush with the said rings and whose middle is of a smaller diameter, this drum or barrel being adapted to limit the transverse curvature of the film under too high effects of tension.

The revolution is obtained by the fact that the shaft 11 is operatively connected either to the delivery or supplying device 3, or to the driving mechanism (not shown) of the said device. The spacing apart of the rings 14 is such that the perforated edges of the film bear upon the said rings when the film is stretched or taut.

I claim:

1. In a device for reducing the tension of the film in cinematographic apparatuses, the combination of a toothed supplying drum disposed at the outlet of the cinematographic apparatus and adapted to drive the film at an almost constant speed, a spool for winding the film, a rotary friction roller between the said drum and the said spool and upon which the film passes and driving means adapted to cause the said friction roller to rotate with a peripherical speed which is different from the average speed of motion of the film and proportional to the said speed.

2. In a device for reducing the tension of the film in cinematographic apparatuses, the combination of a toothed driving drum disposed at the outlet of the cinematographic apparatus and adapted to drive the film at an almost constant speed. a spool for winding the film, a rotary friction roller between the said drum and the said spool and upon which the film passes and driving means adapted to transmit the revolution of the said toothed drum to the said friction roller with a peripheries? speed which is different from that of the said 'lrum and proportional to the said speed.

3. In a device for reducing the tension of the film in cinematographic apparatuses, the combination of a toothed supplying drum disposed at the outlet of the cinematographic apparatus and adapted to drive the film at an almost constant speed, a spool for winding the film, a rotary friction roller between the said drum and the said spool and upon which the film passes and driving means adapted to cause the said friction roller to rotate with a peripherical speed which is different from the average speed of motion of the, film and periphery of the said rings and the middle of which is of a smaller diameter.

In testimony whereof I have hereunto affixed my signature.

ETIENNE OEHMICHEN.

proportional to the said speed, the said friction roller being constituted by a driven shaft, two discs connected to the saidcsha-ft, friction rings upon the said discs, the said rings being disposed so as to support the 

